I sometimes wonder how hard it would be to cut dependency trees to size by finding the largest and most easily replaced or disabled subtrees, including in dependencies (not just the main project). Then upstream those changes if possible, in case of disabled subtrees as optional features with compile-time switches.

I can't imagine that all of the 20 MB of code really need to be there in the binary of a 100 kloc main project which does not rely on anything that is traditionally considered a large software package.